问题描述

我正在尝试在 Windows 窗体中的 ListBox 之间拖放多个项目.我遇到的问题是，如果我选择多个按住 Shift 键的项目并尝试在不释放键的情况下拖放它，我会收到错误消息.实际上 SelectedIndices 和 SelectedItems 只显示 1 个项目，即我首先单击的那个，即使多个项目在 ListBox 中突出显示.

I'm trying to do a drag and drop of multiple items between ListBox in windows forms. The problem I'm having is if I select multiple items holding the Shift key and try to drag and drop it without release the the key I get an error. Actually the SelectedIndices and SelectedItems just show 1 item, the one I clicked first, even though multiple items are highlighted in the ListBox.

我正在使用 SelectionMode = MultiExtended

I'm using SelectionMode = MultiExtended

void ZListBox_MouseMove(object sender, MouseEventArgs e)
{
    if (isDraggingPoint.HasValue && e.Button == MouseButtons.Left && SelectedIndex >= 0)
    {
        var pointToClient = PointToClient(MousePosition);

        if (isDraggingPoint.Value.Y != pointToClient.Y)
        {
            lastIndexItemOver = -1;
            isDraggingPoint = null;

            var dropResult = DoDragDrop(SelectedItems, DragDropEffects.Copy);
        }
    }
}

似乎如果我在执行DoDragDrop"之前不释放鼠标左键，则不会选择项目，并且如果我尝试从另一个 ListBox 获取 SelectedIndices，则计数是选定的项目"，但是当我尝试浏览列表时，我得到一个 IndexOutOfRangeException.

It seems that if I don't release the left mouse button before I do "DoDragDrop", the items aren't selected and also if I try to get the SelectedIndices from the other ListBox, the Count is the number of "selected items", but when I try to navigate the list, I get a IndexOutOfRangeException.

有什么解决办法吗?

重现问题的示例代码:(重现:1- 选择一个项目2- 按住 shift 并单击另一个项目，而不是释放 shift 和鼠标按钮，拖动此项目(如果您在if"中有断点，您将在 SelectedItems 上看到只有 1 个项目))

Sample code to reproduce the issue: (To reproduce: 1- Select an item 2- Hold shift and click in another item, than without release shift and mouse button, drag this item (if you have a breakpoint inside the 'if', you'll see just 1 item on SelectedItems))

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            Load += Form1_Load;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            var someList = new List<ListItemsTest>();
            someList.Add(new ListItemsTest() { ID = 1, Name = "Name 1" });
            someList.Add(new ListItemsTest() { ID = 2, Name = "Name 2" });
            someList.Add(new ListItemsTest() { ID = 3, Name = "Name 3" });
            someList.Add(new ListItemsTest() { ID = 4, Name = "Name 4" });
            someList.Add(new ListItemsTest() { ID = 5, Name = "Name 5" });
            listBox1.DisplayMember = "Name";
            listBox1.ValueMember = "ID";
            listBox1.DataSource = someList;
            listBox1.SelectionMode = SelectionMode.MultiExtended;
            listBox1.MouseMove += ListBox1_MouseMove;
            listBox1.AllowDrop = true;
        }

        void ListBox1_MouseMove(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && listBox1.SelectedIndex >= 0)
            {
                var dropResult = DoDragDrop(listBox1.SelectedItems, DragDropEffects.Copy);
            }
        }

        public class ListItemsTest
        {
            public int ID { get; set; }
            public string Name { get; set; }
        }
    }

推荐答案

只是为了让你知道我找到了另一个解决方案.如果我在 MouseDown 事件中设置 Capture = false，项目将按预期工作，我们不需要手动选择.

Just to let you know I found another solution. If I set Capture = false in the MouseDown event, Items will work as expected and we don't need to do the manual selection.

例如:

void ZListBox_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        Capture = false;
    }
}

希望对你有帮助！

这篇关于ListBox MultiSelect 拖放问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持跟版网！